The rapid increase in vehicle traffic on the roads and the associated queues and travel time extensions are resulting in increased efforts worldwide to identify traffic states and to take them into account for the route selection or for route calculation in navigation systems.
If the geographical coordinates measured using a position-finding method are mapped directly to the coordinate system of a digital map, the true position of the object in the map may differ from the mapped position of the object in the map. The reason is firstly measurement errors in the position-finding method and secondly inaccuracies in the map. Since a navigation system needs to know the true position in the map, the map matching method aligns the measured position with the map information about the position and geometry of objects in the map, so that the most probable position of the object in the map is ascertained.
In vehicle navigation systems, the position of the vehicle is usually measured with the assistance of the satellite position-finding system GPS. The correctness of the measured and actual positions is specified at approximately 15 m in the case of GPS. Similarly, the digital map may have tolerances in the region of meters. For the navigation appliance, it is then necessary to ascertain the position of the vehicle in the digital map so that, by way of example, it is possible to determine a meaningful route calculation from the current location to the destination of travel. Without alignment of the measured position with the map information, the vehicle could find itself outside of the digitalized roads or on the wrong road in the map. Since the position of the vehicle in the digital map is critical for the navigation appliance, the measured position is aligned with the map information such that the most probable location of the vehicle in the map is ascertained for the navigation. In this regard, map matching involves utilizing the knowledge about the movements of the vehicle.
Vehicles are known which send what are known as floating car data (FCD). The system used for this comprises a GPS (Global Positioning System) receiver and a GSM (Global System for Mobile Communication) module. Both modules are already present in many vehicles even without FCD functionality. The GPS receiver measures the position, and the FCD methods use a large amount of these position data to ascertain travel times for the vehicle. The GSM network is used to transmit these travel times as a string of pearls to the traffic data control center. The latter can draw conclusions about the traffic situation from these travel times. In this way, traffic state data are collected for traffic information services.
There are already warnings about queues, for example through TMC, but these are usually not up-to-date enough and there is no information about the position of the end of the queue.
Ends of queues on highways are a major accident blackspot. If, additionally, the end of the queue is difficult to identify or can only be identified very late, the risk of a serious accident is very high. There is therefore a recurrent search for methods of warning the driver about these ends of queues at an early stage.